1. Field of the Invention
This invention relates to a device and method and an engine control unit for determining abnormality of a fuel supply system that supplies fuel stored under pressure in an accumulator to an internal combustion engine and is provided with a fuel pressure sensor for detecting the pressure of the fuel in the accumulator.
2. Description of the Related Art
Conventionally, this kind of device for determining abnormality of a fuel supply system is disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2000-161172. The fuel supply system supplies fuel under pressure by a fuel pump into an accumulator, and detects the pressure of the fuel in the accumulator using a fuel pressure sensor. Further, the fuel supply system determines indicated pressure for the accumulator, and controls the fuel pump such that the fuel pressure detected by the fuel pressure sensor (hereinafter referred to as “the detected fuel pressure) becomes equal to the indicated pressure. Further, the abnormality-determining device determines that the fuel pressure sensor is abnormal when the difference between the indicated pressure and the detected fuel pressure is large.
However, since the conventional abnormality-determining device determines abnormality of the fuel pressure sensor based on the result of comparison between the detected fuel pressure and the indicated pressure, there is a fear that the abnormality is erroneously determined. For example, when an abnormality, such as cracking of the accumulator, occurs, causing the actual fuel pressure in the accumulator to largely drop, the detected fuel pressure becomes much lower than the indicated pressure, even though the fuel pressure sensor is normal. As a result, it is erroneously determined that the fuel pressure sensor is abnormal.